1. Field of the Invention
The present invention pertains to improved methods of insert molding a plastic film or the like over a plastic substrate and to fused film-plastic parts made thereby.
2. Description of the Prior Art
A variety of injection molded parts are made and used for automobile body and trim parts. For example, bumpers, body panels, doors, filler panels, wheel covers, dashboards, arm rests and other parts have been made via injection molding techniques. Additionally, with regard to automobile exteriors, body side moldings, belt line moldings, roof moldings and window moldings are made via injection molding of PVC or other thermoplastic materials.
In order to provide a painted surface for these parts, film lamination techniques have been successfully employed. In accordance with these processes, a paint film laminate is insert molded with the desired thermoplastic to fuse the film over the injection molded part. The resulting injection molded part is ready for assembly without subsequent painting.
The paint film laminate used in these insert molding techniques may comprise a backing sheet to which paint layers are adhered. Typically, the backing sheet comprises an extruded thermoplastic sheet.
In such paint film laminates, a paint film, comprising a cast dried continuous paint coating, is provided over the backing sheet. The paint film may consist of a monocoat, a clear coat over a base coat or a clear coat and a base coat with interposed print or design. The paint film, including base coat, clear coat and print or design, if desired, may range from about 0.5-4 mil. in thickness.
The laminated paint films are available, for example, from Avery Dennison, Automotive Division, or Rexham Decorative Products, Charlotte, N.C. The films are typically provided in a roll, unwound, shaped and trimmed to a proper xe2x80x9cpreformxe2x80x9d size and shape, ready for insertion into an injection mold.
The preform is usually placed along the cavity side of the injection mold with the painted side thereof facing the mold cavity surface. In some instances, the preform may be placed along the core side of the mold. The mold is then clamped and the desired molten resin is injected into the mold cavity. Heat and pressure conditions in the mold partially melt the backing sheet and a melt bonding or fusion of the injected resin and film occur. Injection molds used for these processes are rear or edge gated so that the molten resin is directed along the backside of the film.
Techniques for preforming paint film laminates and insert molding film-plastic parts are disclosed in U.S. Pat. Nos. 5,559,608; 5,746,962; 5,759,477; and 5,783,287. The disclosures of these patents are incorporated herein by reference.
In many cases, it is desired to provide a paint file covered auto or truck part, such as a chin-molding or rocker panel that is adapted for mounting under or over an associated auto or truck body structural part such as a bumper or the like. In many of these structural combinations, a raised portion or boss of the paint film covered auto or truck part is provided in contiguous or closely spaced relation with the associated auto structural part. Due to the close spacing of the boss to the adjacent auto or truck part, the edge of the paint film laminate, overlying this boss region, may separate from the underlying plastic substrate, leading to an unsightly appearance.
Accordingly, there is a need for a method of providing such paint film covered part that will minimize chances of separation of the paint film from its underlying plastic substrate, especially in those regions of the part that are adapted for contiguous or closely spaced position adjacent a mating auto or truck structural or decorative part.
These needs and others are addressed by the instant methods and fused film-plastic parts made thereby. More specifically, parts formed by the present method include show sections which are designed to be visible when the parts are installed on finished assemblies such as automobiles or trucks.
The parts include a show surface section with the paint film laminate overlying the plastic substrate at this section of the part to provide the desired aesthetic appeal. An attachment flange section of the part is provided and is usually hidden from sight when the part is assembled to its associated auto or truck structural or decorative part. This flange serves as a mounting location where clamps, bolts, rivets, or other fastening devices can securely attach the paint film covered part to the auto or truck structure.
A raised portion, such as a boss section, is provided intermediate the show surface and attachment flange. This boss is adapted for contiguous or closely spaced positioning adjacent the auto or truck body or structural part. The boss is completely covered by the paint film with the paint film terminating along the attachment flange.
In accordance with the instant methods, the paint film covered part is generally molded in accordance with conventional co-molding injection techniques wherein molten plastic is injected into the die cavity, usually alongside the rear side of the paint film laminate, forcing the laminate to conform to the desired surface configuration of the molding cavity. In accordance with the invention, a specially configured die cavity combined with a novel positioning of the pain film therein, upon molding, results in the aforementioned paint film covered plastic part.